Comparison of secondary organic aerosol generated from the oxidation of laboratory precursors by hydroxyl radicals, chlorine atoms, and bromine atoms in an oxidation flow reactor
Comparison of secondary organic aerosol generated from the oxidation of laboratory precursors by hydroxyl radicals, chlorine atoms, and bromine atoms in an oxidation flow reactor
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DOI：
10.1039/d2ea00018k
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发表时间：
2022-07-14
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影响因子：
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通讯作者：
Brune, William H.
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文献类型：
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作者：
Lambe, Andrew T.;Avery, Anita M.;Brune, William H.
羟基自由基（OH）作为白天氧化剂的作用在全球范围内得到了很好的确立。在特定的污染源区域，如海洋边界层和受污染的沿海城市，其他白天氧化剂，如氯原子（Cl）甚至溴原子（Br），可能与OH竞争氧化挥发性有机化合物（VOCs）和/或增强大气的整体氧化能力。然而，研究卤素引发的二次有机气溶胶（SOA）形成的研究数量非常有限，导致这些氧化老化过程存在很大的不确定性。在这里，我们表征了氧化流动反应器（OFR）中正十二烷（n-C-12）和甲苯的OH和Cl氧化以及异戊二烯和α -蒎烯的OH， Cl和Br氧化产生的实验室SOA的化学组成和产率。在OFR中，前驱体的氧化使用OH、Cl和Br的综合暴露，暴露范围分别为3.1 × 10（10）至2.3 × 10（12）、6.1 × 10(9)至1.3 × 10（12）和3.2 × 10（10）至9.7 × 10（12）分子cm(-3) s（-1）。与OH一样，在研究的OFR条件范围内，Cl促进了SOA的多步氧化老化。相比之下，br引发的SOA氧化老化程度有限。在OFR研究中获得的SOA元素比和质量产率与在环境室研究中从相同前体的OH和Cl氧化中获得的结果相当。总体而言，我们的研究结果表明，烷烃、芳香族和萜类SOA前体的特点是OH-和卤素引发的SOA产率不同，而Cl可能会增强生物源和人为排放影响区域SOA形成的潜力，Br可能具有相反的作用。
The role of hydroxyl radicals (OH) as a daytime oxidant is well established on a global scale. In specific source regions, such as the marine boundary layer and polluted coastal cities, other daytime oxidants, such as chlorine atoms (Cl) and even bromine atoms (Br), may compete with OH for the oxidation of volatile organic compounds (VOCs) and/or enhance the overall oxidation capacity of the atmosphere. However, the number of studies investigating halogen-initiated secondary organic aerosol (SOA) formation is extremely limited, resulting in large uncertainties in these oxidative aging processes. Here, we characterized the chemical composition and yield of laboratory SOA generated in an oxidation flow reactor (OFR) from the OH and Cl oxidation of n-dodecane (n-C-12) and toluene, and the OH, Cl, and Br oxidation of isoprene and alpha-pinene. In the OFR, precursors were oxidized using integrated OH, Cl, and Br exposures ranging from 3.1 x 10(10) to 2.3 x 10(12), 6.1 x 10(9) to 1.3x 10(12) and 3.2 x 10(10) to 9.7 x 10(12) molecules cm(-3) s(-1), respectively. Like OH, Cl facilitated multistep SOA oxidative aging over the range of OFR conditions that were studied. In contrast, the extent of Br-initiated SOA oxidative aging was limited. SOA elemental ratios and mass yields obtained in the OFR studies were comparable to those obtained from OH and Cl oxidation of the same precursors in environmental chamber studies. Overall, our results suggest that alkane, aromatic, and terpenoid SOA precursors are characterized by distinct OH- and halogen-initiated SOA yields, and that while Cl may enhance the SOA formation potential in regions influenced by biogenic and anthropogenic emissions, Br may have the opposite effect.